1. Field of the Invention
The present invention relates to a reactant in the form of granules for thermochemical systems.
2. Description of Related Art
In the field of thermochemical systems based on the thermal characteristics of the reaction between a solid and a gas, or of the adsorption of a gas on a solid, a mixture is employed of a finely divided material, such as expanded graphite, and of a solid reactant, i.e., active agent, for example a salt, or, correspondingly, an adsorbent such as a zeolite. The mixture of expanded graphite and of this solid, which is the site of a chemical reaction or of a physical adsorption, has many advantages during a chemical reaction or a physical adsorption between the solid and the gas. The expanded graphite is in the form of flakes with a very large specific surface and allows the gas to diffuse even in a confined environment.
Document FR-A-2 547 512 describes a process for carrying out a solid gas reaction, in which a mixture of expanded graphite and of a salt is employed as reaction site of a thermochemical system, this mixture being in pulverulent form. This mixture makes it possible to fill reaction chambers of a thermochemical system which are irregular or nonrectilinear in shape. However, the thermal conductivity of the mixture, while higher than that of a salt, is too low to enable the thermochemical systems to achieve satisfactory performance levels. In addition, the charging of a reaction chamber with a pulverulent mixture of expanded graphite and of salt is a difficult operation, since the two components tend to segregate.
In document WO 91/15292 it has been proposed to produce an active composite by preparing a support formed by a block of recompressed expanded graphite which is subsequently impregnated from the outside, for example, with a solution of an active agent, for example a salt, the impregnated support being subsequently dried to produce the active composite. The active composite thus produced has a thermal conductivity which is markedly higher than that of the expanded graphite in flake form, while retaining a high porosity to gas flow.
Despite undoubted advantages, the active composite prepared according to the process described in document WO 91/15292 is not entirely satisfactory. In fact, since this active composite is in the form of rigid blocks which are generally of a cylindrical shape, the reaction chambers intended to receive such a block are limited to rectilinear shapes.
In addition, in order to make it possible to ensure certain applications, it would be appropriate to have a supple or flexible reaction chamber. An active composite in the form of rigid blocks does not allow such reaction chambers to be filled.